We already know that hydrogen is a green fuel that can power automobiles. The catch is that hydrogen is dangerous to store both at fueling stations and aboard the vehicle. The catalyst material used in a hydrogen fuel cell is often platinum or other rare and very expensive metal. A team of researchers from the University of Texas at Dallas and Washington State University think that they may have found a much cheaper catalyst material to advance the adoption of fuel cell technology.

The new catalyst material that the researchers are investigating is a doped aluminum alloy surface. The aluminum alloy is doped with titanium. The titanium is used sparingly in the new catalyst material.

Using controlled temperatures and pressures the team studied the titanium doped aluminum surface searching for signs of catalytic reactions taking place near the titanium atoms. To discover the catalytic reaction the team used the stereoscopic signature of carbon monoxide added to the test to specifically help locate signs of a reaction.

Mercedes-Benz B-Class hydrogen fuel cell vehicle

"We've combined a novel infrared reflection absorption-based surface analysis method and first principles-based predictive modeling of catalytic efficiencies and spectral response, in which a carbon monoxide molecule is used as a probe to identify hydrogen activation on single-crystal aluminum surfaces containing catalytic dopants," says lead researcher Yves J. Chabal of the University of Texas at Dallas.

The titanium added to the aluminum advances the process by helping hydrogen bind to aluminum to form aluminum hydride. When used as a fuel storage device, aluminum hydride could be made to release the hydrogen stores it holds by raising the temperature of the storage medium.

Yeah, if you make a big chart of all naturally occurring hydrocarbons, and sort it by most hydrogen atoms vs. least volume at room temperature, guess what you find at the top? Diesel, gasoline, and kerosene, with alcohols not far behind. We've basically come full circle. Petroleum-based fuels were deemed bad, and pure hydrogen was suggested as an alternative. But pure hydrogen has massive problems with storage and volumetric energy density. If you then look at hydrogen compounds with high energy density and which store easily, you find that the best candidates are... petroleum-based fuels.

If there's going to be a green hydrocarbon-based fuel, it's most likely going to be biofuels. Photosynthesis is basically hydrolysis. Plants take H2O, combine it with energy from sunlight and CO2 to separate out the hydrogen atom to create O2 and sugars (CH2O)n. Those sugars can then be decomposed into alcohols (Cn H2n+1 OH) and hydrocarbons (Cn H2n+2). Instead of building all sorts of fancy equipment and burning electricity to split hydrogen from water, why not just grow a bunch of plants to do it for you?

The one area of hydrogen fuel research which may pan out is using fuel cells instead of an internal combustion engine. The ICE is limited by thermodynamics to about 35%-40% efficiency in something the size of a car (that is, 40% of the energy in the fuel spins the engine, 60% gets converted into waste heat). Fuel cells have exceeded 90% efficiency in the lab, with more practical versions hitting about 60%-70%. But as for hydrogen as a fuel, I don't see it becoming green unless we either massively expand either our biofuel capacity (cheap fuels for hydrogen fuel cells) or our nuclear capacity (cheap electricity for hydrolysis).

There are a number of flies in the ointment when it comes to Hydrogen fuel cells that are constantly glossed over. The hype tends to exceed the reality.

1) Storage and transportation of hydrogen. The best viable storage mechanism is compressed gas in high pressure cylinders. Compressing the hydrogen cost you about 12% of the embodied energy in the hydrogen. However the density is still so low that it would take 20 tanker trucks of hydrogen to transport the same amount of effective fuel as 1 tanker of gasoline. This increases the cost of the fuel. Even pumping gaseous hydrogen in pipelines is surprising energy intensive because of the very low density and can consume a significant amount of the embodied energy. Liquifying isn't really an economical option because it takes 30% of the embodied energy in the hydrogen to liquify it and then you also have cryogenic boil-off issues. Storage by adsorption in solid materials (eg Paladium) is an interesting phenomenon but all the materials that can adsorb a significant amount of Hydrogen also bind quite strongly to it and it takes a significant amount of energy to release the hydrogen. Again you lose too much efficiency. Also the storage density is low.

2) Cost of hydrogen production - Currently almost all commercial hydrogen is derived from steam reformation with Natural gas. This is fairly efficient at around 80%, but converting natural gas to hydrogen and running it in a fuel cell is still less efficient well to wheels than a diesel hybrid car. If you want to get away from fossil fuel sources of hydrogen things get a whole lot worse. If you try to do electrolysis of water it's only around 50% efficient, however after you add in the extra required steps of drying the gas and compressing it and all the other details actual Hydrogen electrolysis systems for generating vehicle fuel consume about 75-80 Kwh per kilogram of H2 produced. In an automotive fuel cell you can recover only about 16 Kwh from that kilo of hydrogen. This is only a 20% system efficiency,and again it negatively effects the fuel cost. Battery powered cars on the other hand can achieve about 90+% efficiency. Batteries of course have their own problems in costs, weight, and longevity.

3) Fuel cell efficiency quotes are often misleading. 90% Laboratory efficiency numbers have almost no relation to real world numbers for an automotive fuel cell because they are achieved at incredibly low current densities. You have to run much higher current densities for an actual fuel cell that has the weight and size constraints needed to fit in a car. Actual efficiencies are more on the order of 50-55%.

4) Expensive. Currently the catalyst of choice is platinum. It achieves the highest efficiencies. Much effort has been put into finding cost effective alternatives and there are some but they all perform significantly less efficiently that platinum. All the top end efficiency numbers you see are with platinum catalysts.

5)Catalyst poisoning. The source of oxygen to run the fuel cell comes from the air, unfortunately there are a number of sulfur and nitrogen compounds in the air also that poison the catalyst and degrade the capacity and efficiency of the fuel cell. This vulnerability is an additional headache.

6)Infrastructure - or lack of. To build up a wide scale hydrogen fuel delivery infrastructure will cost into the Trillions of dollars. You have a chicken and egg problem, Fuel cell cars and a widespread fueling infrastructure to fuel them, we have neither and can't afford to build them.

If you include all the losses from well to wheels, even though IC engines only have about 30-40% efficiencies, the much lower losses in the rest of the fuel chain mean that fuel cells are actually less efficient over all.

Fuel cells still have a broad appeal though probably because the paradigm of a 'gas' tank and fueling up at a station like we do now with gas is something we are already comfortable with. Fuel cells are in reality just another form of a Battery. The difference being that if you double the size of the 'gas' tank in a battery powered car you double the cost, doubling the size of the tank in a fuel cell vehicle is much less costly. The basic problem though is that production and delivery of Hydrogen is just too expensive and is constrained by physics from significant improvement.

As for Biofuels, I find it very disturbing that nobody addresses the problem that our fresh water supplies are already maxed out. There is no fresh water to supply the enormous requirements that growing biofuels on a significant scale would require. Nor is soil erosion losses addressed. To achieve economical yields per acre requires intensive tilling and soil loss rates at 1 inch per 10-20 years. Topsoil replacement rates are around 1 inch in 500 years. It's sacrificing our future farm land for fuel, it's not sustainable.If you go with covered aquaculture your infrastructure costs go up and you might as well go with solar panels. The only viable biofuels growth areas seem to be the oceans./rant off

quote: As for Biofuels, I find it very disturbing that nobody addresses the problem that our fresh water supplies are already maxed out. There is no fresh water to supply the enormous requirements that growing biofuels on a significant scale would require. Nor is soil erosion losses addressed. To achieve economical yields per acre requires intensive tilling and soil loss rates at 1 inch per 10-20 years. Topsoil replacement rates are around 1 inch in 500 years. It's sacrificing our future farm land for fuel, it's not sustainable. If you go with covered aquaculture your infrastructure costs go up and you might as well go with solar panels. The only viable biofuels growth areas seem to be the oceans.

I'm not sure about the fresh water supply being maxed out. Maybe in certain areas but not everywhere. You could simply build offshore structures out past the point where the Mississippi River empties into the Gulf of Mexico, then pump fresh water from the river, through the biofuel growing platform with the excess going into the Gulf, it would still end up at the same place only take a different course.

Also if you are using algae for the biofuel production then there shouldn't be any problem with topsoil erosion, since that type of facility can be placed anywhere, on an offshore platform, on rocky less fertile ground, or even on rooftops of industrial plants. If you place an algae biofuel plant on top of a building you would shade the building by capturing the sunlight used to produce the fuel which would lower the energy needed to cool the building. It will take a little creative thinking but overall I believe biofuels can be made to work without too large an impact on the environment.

The problem lies in the sheer scale of biofuel production needed. Energy capture and storage by plants is very low in efficiency. Coupled with the enormous fuel requirements we have dictates fresh water requirements far beyond any available supply. I agree that algae has probably the best potential of the biofuels and that seawater based algae may be the only potentially workable direction for biofuel production.

Unfortunately with conversion efficiencies so low, area requirements so large, and the energy and materials costs to harvest and economically extract from such a low density energy source the problems are formidable.

There are many alternative energy sources that are technically feasible, but very few of those are economically feasible, and even fewer can be accommodated within our sustainable resource limits. Any workable solution must meet all three requirements. Biofuels may supply a small percentage of the energy puzzle, but it currently doesn't look to good at large scales.

It's a difficult problem with no clear winning answers, and anybody who tells you there is a clear solution is just ignorant of the over all picture. The clear answers evaporate before you when you look into the details.

Using methane via steam reformation in a PEM or PAFC fuel cell is a much cleaner and more efficient way to produce power than by burning it in a large power generation plant. Only 20-30% less CO2, and no other pollutants at all. It has just been more expensive. The Bloom Box 100 kW SOFC are even more expensive but even more efficient. And SOFC technology has the potential to get much cheaper very quickly - Bloom's customers include FedEx, BofA, Google, Apple, WalMart, and others. They are just one of many global SOFC developers (Ceres, CFCL, SOFCpower, Acumentrics, Topsoe,...) including Lilliputian making a 10-100 watt SOFC on a chip.